AR: Google Shopping Feed Pro

I don't know if this app fits all merchants needs, but it certainly fits ours.
Their customer service is second to none, with an incredibly fast response time and very professional and helpful answers.
We implemented the feed on one of our websites almost a year ago, and since it does exactly what we need, we're implementing it on all our other sites.
Oh, and by the way, it's the sole and only paid app we use... so to say that if we decided to use this app and not code it ourselves, it's for a good reason!